1. Field of the Invention
This invention relates to an air bag inflation gas generator to feed gas for inflation of air bags such as air bags for absorbing collision shocks, life jackets, rubber, rafts, and escape chutes.
2. Description of the Prior Art
A prior shock absorber to protect a car driver from shocks at collision accidents comprises an air bag, for example, having a capacity of 60 liters and a gas generator to inflate the air bag with gas. At a collision accident, explosives or other gas generating agents having a similar composition thereto, which are charged in the gas generator, are ignited and burnt to produce some gas. The air bag is instantaneously inflated by the resultant gas for driver protection against any collision shocks, which can avoid possible serious injury.
FIG. 13 shows a prior air bag inflation gas generator disclosed in the Japanese Patent Laid-open No. 2-155857. In the drawing, the reference numeral 11 shows a combustion chamber accommodating a plurality of layers of gas generating agents 13.
The gas generating agents 13 have disc-like construction having a through hole 15 in the center thereof and the through hole 15 contains an ignition agent 17. These gas generating agents 13 are contained in a sealed vessel 19 which has a recess 21 in the center thereof denting into the through hole 15 in the gas generating agents 13. An igniter 23 for combustion of the gas generating agents is installed in the recess 21. A combustion chamber filter 25 is provided along the inner wall of the combustion chamber 11, and a plenum chamber 27 into which gas flows through orifices 26 after passing through the combustion chamber filter 25 annularly surrounds the combustion chamber 11. The plenum chamber 27 contains plenum chamber filters consisting of an upper filter 29 and a gas filter 31. The plenum chamber 27 further includes gas outlets 33 to feed the gas into an air bag through the gas filter 31.
In this type of air bag inflation gas generator, when an electric current is applied to the igniter 23, the ignition agent 17 burns by burning of explosives in the igniter 23. This burning causes the gas generating agents 13 to burn and the resultant gas flows into the plenum chamber 27 through the combustion chamber filter 19 arranged along the inner wall of the combustion chamber 11. The gas is purified by the upper filter 29 and the gas filter 31 and flows into the air bag through the gas outlets 33. The air bag can be inflated completely within a very short time, for example, approximately 0.04 second.
In this prior air bag inflation gas generator, volume of combustion gas generated from the gas generating agents 13 and furthermore purification efficiency for the combustion gas have limits.
Particularly for inflation of an air bag for a front passenger seat, a large capacity air bag being about 2.5 times, for example, as much as a prior air bag for a driver is necessary because passenger condition of the front passenger seat is different from the driver's with the result that the passenger does not have a certain position and the passenger varies in physique from a child to an adult. There was demanded an air bag inflation gas generator supplying a large volume of gas generated from the gas generating agents and furthermore able to purify such a large volume of gas completely.
In the Japanese Patent Laid-open No. 1-297336, an air bag inflation gas generator having a construction in which gas generating agents are installed in the center of a cylinder and to be burnt by an igniter for feeding a combustion gas through gas outlets at the cylinder into the air bag is disclosed. In this generator, the gas outlets formed at the cylinder cause the combustion gas to flow into the air bag more efficiently than the prior art. However, because the gas generating agents are tablet in shape, the combustion surface area of the gas generating agents at the start of burning is large, resulting a large volume of gas, which causes a problem that the air bag is abruptly inflated.
In the Japanese Patent Laid-open No. 1-289736, an air bag inflation gas generator having two or more generators for a driver mounted on a specified pedestal is disclosed. In this equipment, because two igniters are used, ignition of them can be controlled. However, two or more generators installed for a driver prevent decrease in weight and size. Therefore, a large volume of combustion gas can not be fed into an air bag effectively.